Energy storage device

Abstract

An energy storage device comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a nonaqueous electrolyte, and an insulating layer disposed between the positive electrode and the separator, wherein the positive electrode contains a compound represented by Li a Ni b Co c M d W x Nb y Zr z O 2 (provided that a, b, c, d, x, y and z satisfy the equations of 0≦a≦1.2, 0≦b≦1, 0.1≦c≦0.4, 0≦d≦0.5, 0≦x≦0.1, 0≦y≦0.1, 0≦z≦0.1 and b+c+d=1, and M denotes at least one kind of element selected from the group consisting of Mn, Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, Sn and Mg) as a positive active material and the negative electrode contains hardly graphitizable carbon with a D50 particle diameter greater than or equal to 1.0 μm and less than or equal to 6.0 μm as a negative active material.

What is claimed is: 
     
         1 . An energy storage device comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a nonaqueous electrolyte, and an insulating layer disposed between the positive electrode and the separator,
 wherein the positive electrode contains a compound represented by Li a Ni b Co c M d W x Nb y Zr z O 2  (provided that a, b, c, d, x, y and z satisfy the equations of 0≦a≦1.2, 0≦b≦1, 0.1≦c≦0.4, 0≦d≦0.5, 0≦x≦0.1, 0≦y≦0.1, 0≦z≦0.1 and b+c+d=1, and M denotes at least one kind of element selected from the group consisting of Mn, Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, Sn and Mg) as a positive active material and the negative electrode contains hardly graphitizable carbon with a D50 particle diameter greater than or equal to 1.0 μm and less than or equal to 6.0 μm as a negative active material.   
     
     
         2 . The energy storage device according to  claim 1 , wherein the negative electrode includes a negative substrate layer and a negative composite layer containing the negative active material on the negative substrate layer, and the proportion of a D90 particle diameter of the negative active material to the thickness of the negative composite layer disposed at one side of the negative substrate layer is greater than or equal to 0.07 and less than or equal to 0.7. 
     
     
         3 . The energy storage device according to  claim 1 , wherein the positive electrode includes a positive substrate layer and a positive composite layer containing the positive active material on the positive substrate layer, and the insulating layer is bonded to the separator and is not bonded to the positive composite layer. 
     
     
         4 . The energy storage device according to  claim 1 , wherein the negative electrode includes a negative substrate layer and a negative composite layer containing the negative active material on the negative substrate layer, and the proportion of a D90 particle diameter of the negative active material to the thickness of the negative composite layer disposed at one side of the negative substrate layer is greater than or equal to 0.12 and less than or equal to 0.44. 
     
     
         5 . The energy storage device according to  claim 1 , wherein the insulating layer is constituted of a resin containing inorganic particles. 
     
     
         6 . The energy storage device according to  claim 4 , wherein the positive electrode includes a positive substrate layer and a positive composite layer containing the positive active material on the positive substrate layer, and the insulating layer is bonded to the separator and is not bonded to the positive composite layer. 
     
     
         7 . The energy storage device according to  claim 4 , wherein the positive electrode includes a positive substrate layer and a positive composite layer containing the positive active material on the positive substrate layer, and the insulating layer is bonded to the separator and is not bonded to the positive composite layer. 
     
     
         8 . The energy storage device according to  claim 2 , wherein the insulating layer is constituted of a resin containing inorganic particles. 
     
     
         9 . The energy storage device according to  claim 3 , wherein the insulating layer is constituted of a resin containing inorganic particles. 
     
     
         10 . The energy storage device according to  claim 4 , wherein the insulating layer is constituted of a resin containing inorganic particles. 
     
     
         11 . The energy storage device according to  claim 6 , wherein the insulating layer is constituted of a resin containing inorganic particles.